Yosr Zaouali

Chemical composition and antimicrobial activity of the essential oils from four Ruta species growing in Algeria

Antimicrobial properties of plants essential oils have been investigated in order to suggest them as potential tools to overcome the microbial drug resistance and the increasing incidence of food borne diseases problems. The aim of this research is to study the antibacterial and antifungal effects of four traditional plants essential oils, Ruta angustifolia, Ruta chalepensis, Ruta graveolens and Ruta tuberculata, against standard bacterial and fungal strains. The chemical compounds of the oils were examined by GC/MS. Results revealed a powerful antifungal activity against filamentous fungi. Aspergillus fumigatus and Cladosporium herbarum are the most sensitive strains to these oils with MIC values less than 3.5 μg ml(-1) for certain oils, reaching 7.8 μg ml(-1) for other. GC/MS essay exhibited ketones as the most abundant constituent of these oils except for R. tuberculata essential oil which has a completely different composition, monoterpenes alcohols being the most abundant. These compositions explain their potential antifungal activity.

Variation of the Chemical Composition of Essential Oils in Tunisian Populations of Thymus algeriensisBoiss. et Reut. (Lamiaceae) and Implication for Conservation

The variation of the essential‐oil composition among 14 Tunisian natural populations of Thymus algeriensis Boiss. et Reut. (=Thymus hirtus Willd. ssp. algeriensis Boiss. et Reut.) was assessed by GC (RI) and GC/MS. The populations were collected from different geographical regions belonging to the sub‐humid, upper semi‐arid, mean semi‐arid, lower semi‐arid, and upper‐arid bioclimates. A total of 47 constituents, representing 81.0 to 96.5% of the total oil, were identified. The main volatiles at the species level were 1,8‐cineole (17.7%), α‐pinene (15.5%), and camphor (8.2%). A high variation among populations for the majority of the compounds was shown. Camphor (0.2–14.0%), linalool (0.2–22.4%), borneol (<0.01–24.3%), caryophyllene oxide (<0.01–18.8%), thymol (<0.01–54.9%), γ‐terpinene (0.4–6.5%), α‐copaene (0.4–7.6%), linalyl acetate (<0.01–6.4%), and methyl eugenol (<0.01–6.9%) were the main constituents differentiating the populations. The chemical differentiation among populations, assessed by principal component analysis (PCA) and a UPGMA (unweighted pair‐group method with averaging) cluster analysis performed on all populations and compounds, was high. Six chemotypes according to the main compounds have been distinguished, i.e., caryophyllene oxide/1,8‐cineole/α‐pinene, 1,8‐cineole/α‐pinene, 1,8‐cineole/α‐pinene/camphor, borneol/1,8‐cineole/α‐pinene, linalool, and thymol chemotypes. The spatial chemotype distribution was linked to the geographic distance among populations rather than to bioclimates, indicating that local selective environmental factors act on the chemotype diversity.

Essential Oil Variation among Natural Populations of Lavandula multifida L. (Lamiaceae)

Volatiles from twelve wild Tunisian populations of Lavandula multifida L. growing in different bioclimatic zones were assessed by GC (RI) and GC/MS. Thirty‐six constituents, representing 83.48% of the total oil were identified. The major components at the species level were carvacrol (31.81%), β‐bisabolene (14.89%), and acrylic acid dodecyl ester (11.43%). These volatiles, together with α‐pinene, were also the main compounds discriminating the populations. According to these dominant compounds, one chemotype was revealed, a carvacrol/β‐bisabolene/acrylic acid dodecyl ester chemotype. However, a significant variation among the populations was observed for the majority of the constituents.

Genetic variation in Tunisian melon (Cucumis melo L.) germplasm as assessed by morphological traits

The morphological variation and the systematical status of 28 traditional melon including two ancient varieties collected from different geographical and bioclimatic areas of Tunisia were assessed based on 34 qualitative and quantitative traits. Yellow Canary was used as a reference variety. Significant differences among accessions within and among sites of collection were revealed for the majority of traits. The accessions from the Sahel were more polymorphic than those from Tozeur’s oasis. However, the classification of the local accessions according to Munger and Robinson’s varietal groups did not allow clear segregation of several of them because of their high heterogeneity. The principal component analysis (PCA) performed on all measured traits, allowed a distinction among the introduced varieties clustered according to their varietal group, and the local accessions grouped separately according to their geographical origin and bioclimatic zone. Mahalanobis distances among PCA’s groups were significant. The correlation found between Mahalanobis distance matrix and geographical distance matrix among origins corroborated isolation per distance. Conservation strategies should be made appropriately according to origins. Accessions from the Sahel showing the highest polymorphism within and among sites of collection should be firstly preserved.

Chemical profiles and antioxidant activities of the essential oils of two medicinal plant species grown in Tunisia

A comparison of leaves essential oil composition and antioxidant activity of the two medicinal plant species Juniperus oxycedrus and Juniperus phoenicea grown in Tunisia is reported in this study. The highest yield of essential oil was recorded for J. phoenicea (0.34%, w/w) whereas J. oxycedrus exhibited the lowest yield (0.18%). Qualitative and quantitative variations in the composition of oils according to species were shown. Tunisian sample of those species are especially rich of β-phellandrene. Based on both tests DPPH (2,2-di-phenyl-1-picrilhydrazyl) and FRAP (ferric reducing antioxidant power), the two species presented high levels of antioxidant capacities. The DPPH test shows the highest antioxidant activity (ic 50=20.1±0.1 μg/mL) for the species J. oxycedrus while J. phoenicea presented the lowest antioxidant activity (ic 50=25.4±0.3 μg/mL). The highest level of ferric reducing ability of volatile oils is recorded for J. oxycedrus (15.90±0.87 μmol Fe2+/g), whereas J. phoenicea exhibits the lowest level (10.99±0.52 μmol Fe2+/g).